In the parse_many function, we have one thread doing the stage 1, while the main thread does stage 2. So if stage 1 and stage 2 take half the time, the parse_many could run at twice the speed. It is unlikely to do so. Still, we see benefits of about 40% due to threading.
To achieve this interleaving, we load the data in batches (blocks) of some size. In the current code (master), we create a new thread for each batch. Thread creation is expensive so our approach only works over sizeable batches. This PR improves things and makes parse_many faster when using small batches.
This fixes our parse_stream benchmark which is just busted.
This replaces the one-thread per batch routine by a worker object that reuses the same thread. In benchmarks, this allows us to get the same maximal speed, but with smaller processing blocks. It does not help much with larger blocks because the cost of the thread create gets amortized efficiently.
This PR makes parse_many beneficial over small datasets. It also makes us less dependent on the thread creation time.
Unfortunately, it is going to be difficult to say anything definitive in general. The cost of creating a thread varies widely depending on the OS. On some systems, it might be cheap, in others very expensive. It should be expected that the new code will depend less drastically on the performances of the underlying system, since we create juste one thread.
Co-authored-by: John Keiser <john@johnkeiser.com>
Co-authored-by: Daniel Lemire <lemire@gmai.com>
* This is an implementation of "size()" for arrays and objects.
* Adding benchmark
* Adding a size() remark in the documentation.
* Extending size() to result types.
* It is inconvenient to be unable to print a padded_string.
* Allows us to print the padded_string even when it is embedded in result object when exceptions are enabled.
* Fallback should use our scalar code.
* parse should have a nicer error message.
* Making it so that "minify" can use different architectures.
* Let us change the minifier competition so that it tests all implementations.
* Documenting the untaken optimization opportunity.
Co-authored-by: John Keiser <john@johnkeiser.com>
Daniel Lemire
Daniel Lemire
John Keiser